1. Field of the Invention
The present invention relates to the removal of organic and inorganic deposits from contact lenses, particularly soft contact lenses. More specifically, this invention relates to an aqueous solution for removing contact lens deposits made up of materials such as proteins, mucins, lipids and calcium, and to a method of cleaning contact lenses using this solution.
2. Description of Related Art
The solution and method of the present invention have been found to be particularly effective in removing unwanted deposits from soft contact lenses. Although this invention is not directly related to the manufacture of soft contact lenses, it should be noted that various materials and methods have been described in the prior art for use in the manufacture of these lenses. For example, U.S. Pat. Nos. 2,976,576 and 3,503,393 describe the use of hydrophilic or partially hydrophilic plastic materials commonly known as polymeric hydrogels for the manufacture of soft contact lenses. Specifically, these two patents relate to the manufacture of three dimensional polymeric hydrogels from poly(hydroxyethyl methacrylate) in aqueous media. These lenses have a cross-linked polymeric hydrogel structure and the appearance of an elastic, soft and transparent hydrogel. Various other materials may also be utilized for the manufacture of soft contact lenses, such as silicones or other optically suitable flexible polymers.
One of the problems connected with the use of soft contact lenses is the formation of unwanted deposits made up of organic and/or inorganic materials on the lenses when the lenses are worn on the human eye. This problem is especially troublesome when the lenses are worn for extended periods. These deposits normally comprise proteinaceous material, mucins, lipids and calcium. The deposits may be located both on the surface and below the surface of the lens, and may be strongly bound to the polymeric hydrogel. The presence of these deposits on the surface and beneath the surface of the lens can cause considerable discomfort and other symptomology to the wearer of the lens.
The above-described deposits can be quite difficult to remove from the lens due to the presence of deposits beneath the surface of the lens and the strong bond between the deposits and the polymeric hydrogel of the lens. The deposits present on the surface of the lens are more readily removed than are the deposits beneath the surface of the lens. U.S. Pat. No. 4,311,618 describes the use of chemical cleaners to remove cross-linked (denatured) proteins from lens surfaces. Various enzymatic preparations for removing contact lens surface deposits are also available. For example, U.S. Pat. No. 3,910,296 describes the use of proteolytic enzymes such as papain for the removal of proteinaceous material from the lens surface, and U.S. Pat. No. 4,096,870 describes the use of pancreatin for the removal of surface deposits consisting of proteinaceous material, mucins and lipids; pancreatin is an enzyme complex having proteolytic, lipolytic and amylolytic activity. However, deposits beneath the surface of the lens are generally difficult to remove by means of enzyme treatment alone. Furthermore, the sub-surface deposits are generally difficult to remove mechanically, such as by rubbing the lens. Thus, it is apparent based on the foregoing description that there is a need for a preparation which is capable of removing both surface and sub-surface deposits from soft contact lenses.
Applicant has discovered that sub-surface deposits can be effectively removed by means of chemical treatment. More specifically, applicant has discovered that these deposits can be effectively removed by soaking the lens in an aqueous solution containing a mixture which includes a surfactant, a calcium chelating agent and a source of hydrated protons, and optionally also urea; this discovery is described in detail in applicant's copending application entitled "Solution and Method for Removing Protein, Lipid, and Calcium Deposits from Contact Lenses", which application was filed concurrently with the present application (now U.S. Pat. No. 4,599,195). The lens cleaning solution of the present invention differs from the solution described in the above-cited copending application in that, inter alia, the former solution comprises a combination of chemical and enzymatic cleaning components.